text:
How do PPL, CPL, and ATPL compare?
What are hiding under these letters?
What do they stand for?
I have read many others, but I could never understand what they mean and the pilot's career on each of them.
If possible, can anyone post a brief list and their tasks and responsibilities, please?

Nobody has mentioned experience specifics.
You can get a PPL in about 35 flying hours. It is really a licence to learn how to fly, but without being paid to do so.
You can get a CPL in about 250 flying hours. This also is a licence to learn how to fly, but while being paid to do so. This is also much more difficult to earn, involving much higher precision flying and a ton more knowledge.
You can get an ATPL in about 1,500 flying hours. It is a licence that tells professional pilots you have now learned the basics of how to fly an airplane.
Having said that, a pilot never stops learning, every type they add requires extensive training, and MOST commercial pilots come close to killing themselves about five times during their career.
Commercial pilots also have to prove they still have their skills - and their health - every six months.

Jim, not exactly the case in the US. The minimum number of hours for a PPL is 40 and most pilots need around 60. Commercial pilots need 100 hours of PIC time, so probably more like 150 at a bare minimum. Multi engine commercial need 250 hours. A commercial license isn’t much good without an instrument rating, so you need that as well. Commercial pilots need a medical every 12 months, ATPs 6 months. If you are a commercial Part 91 pilot you only need to have your skills checked every 24 months—just like PPL. Airlines and Part 135 operations check the skill levels depending based on OpSpecs.

@JScarry No. US FAA: PPL for ASEL can be earned in 40hours if completed under part 61; 35hours for part 141 flight schools.  PPL for AMEL is 20hours more for part 141 flight schools.  CPL for ASEL in 250hours if completed under part 61; 120hours for part 141 flight schools. CPL for AMEL in 55 hours more. ATPL in 1,500 hours regardless of part 61 or 141. 14 CFR 61 Subpart E (61.103) spell out PPL reqs for ASEL and AMEL; Subpart F (61.123) for ASEL and AMEL CPL reqs. 14 CFR 141 Part F, Appendix B spells out Part 141 PPL reqs for ASEL and AMEL; Appendix D for ASEL and AMEL CPL.

Manuel, I had forgotten about Part 141 as I don”t know anyone who has done it. Good catch.

I think the CPL difficulty is being overstated a bit.  The hardest part about it is finding a complex airplane (especially for SEL).  The maneuvers are excellent training, but not especially difficult and the extra knowledge required is not all that much.  Adding IFR is a much bigger knowledge jump.

PPL is a "Private Pilots License" and is a qualification which allows you to act as Pilot in Command in an aeroplane [PPL(A)] or Helicopter [PPL(H)] without remuneration. It is the most common license held in general aviation, and is the first step to all the other licenses that you mentioned in your question.
CPL is a Commercial Pilots License, and allows you to act as Pilot in Command of a charter or corporate flight.
ATPL (or ATP Certificate) is an Airline Transport Pilots License and is the highest level of pilot certification.

"and is the first step to all the other licenses that can be obtained." Except for Sport and Recreational licenses.

@RonBeyer - yes, that should have read "[...] that you mentioned"

And technically, you don't have to get a PPL first.  When I got my multi-engine rating, I had my single engine PPL and took the commercial multi-engine checkride, so never had a multi PPL.  In fact, I now have Multi ATP with private single-engine privileges, lol.  The same could be done for your first checkride.

PPL
Private Pilot License. You may fly your own plane or rent one to fly. You can fly families and friends. You can not be paid to fly.
CPL
Commercial Pilot License. You can be paid to fly, but usually in small planes only. Typical activities include aerial photography, banner towing, dropping sky divers, etc.
ATPL
Airline Transport Pilot License. You can act as captain of a large airliner.

To give a rough perspective, PPLs usually fly small single-engine propeller planes; CPLs fly slightly larger planes that carry maybe 20~50 people, ATPLs are the ones that fly Airbus and Boeings.
Note that the pilot license restricts which kind of aviation activity a pilot can fly, but does not restrict the size or speed of the aircraft. Technically you can fly an A380 with a PPL if you fly it privately, but very few people (if any!) do that.
In the simple sense, PPL must be acquired before CPL, and CPL before ATPL. It is like driving licenses: you must get an ordinary driving license before you can drive a bus, and you better can drive a bus before you want to drive a semi-trailer. The higher privilege licenses require better precision, better proficiency and handling more complex aircraft systems.
Obviously, pilot and driving licenses vary country by country, but I feel this answer address the OP's concerns.

If I understand correctly, I could fly that A380 on my PPL, but I would need endorsements for a complex aircraft and multi-engine, or something along those lines?

@FreeMan It's also multi-crew, which complicates things.

@reirab, yeah, but if I'm taking it for a joy-ride, none of that really matters, does it?  :D

In the U.S., you're also required to have an ATPL to act as any required flight crew member in a scheduled airline operation. However, in some other countries (including EASA-land, as far as I know,) it's not only possible, but common to fly as SIC on a large airliner without an ATPL. For example, the pilot who crashed the Germanwings A320 flight had only a CPL and a bit over 600 hours logged.

@FreeMan You would need a type rating, complex, and multi-engine. Since it is not certified for single-pilot operations, you need a similarly qualified copilot. If you go above 18000, you also need an IFR rating. But yes, it is technically possible to fly a transport category aircraft with a PPL and appropriate ratings. Just ask John Travolta or Bruce Dickinson

just being pedanting now, but for ATPL I would replace 'captain of large airliner' with 'you can be PIC of a multi-crew aircraft'

@RonBeyer Don't forget about your high altitude endorsement!  ;-)

PPL - PRIVATE PILOT CERTIFICATE
This is the lowest grade of pilot certificate which allows a user to operate an aircraft in all areas of the National Airspace System with limited provisions.  Along with a Third Class Medical Certificate, it allows the holder to act as PIC in all categories and classes of aircraft, or on type rated large or turbojet powered aircraft.  Use of a PPL along with a Basic Med is permissible as well, provided operations are restricted to the limitations in §61.113(i).  A PPL also allows the holder to tow gliders, conduct factory test flights, and demonstrate aircraft to prospective buyers under the limitations in Part 61.  It also has limited provisions available to serve as PIC for compensation or hire as detailed in §61.113.
CPL - COMMERCIAL PILOT CERTIFICATE
This is the next grade of pilot certificate up from Private Pilot.  It allows all the privelages of a PPL plus, when combined with a valid Second Class or higher Medical Certificate, a CPL allows the holder to serve as PIC while carrying persons or property or to fly for compensation or hire under the areas listed in §119.1(e).  It does not permit the holder to fly in operations which involve holding out for common carriage such as a part 121 scheduled air carrier or a part 135 charter or commuter operation.  Along with an instrument rating for either airplane, helicopter, or powered lift, it is also a pre-requisite to apply for either an Airline Transport Pilot or Flight Instructor Certificates.
ATPL - AIRLINE TRANSPORT PILOT CERTIFICATE
This is the highest grade of pilot certificate issued in the United States.  They are only issued for the Airplane, Helicopter or Powered lift categories of aircraft as well as specific type ratings.  In addition to all the privileges of a CPL and, when combined with a First Class Medical Certificate, it allows the holder to exercise privileges of PIC and SIC in scheduled air carrier, charter and commuter services if either the holder or the holder’s employer also holds a valid Part 121 air carrier certificate or Part 135 charter or commuter certificates.  It also permits limited flight instruction within the holder or holder’s employer’s Part 121 or 135 certificates on an aircraft the holder is type rated on under the operation.

Uk & Europe minimum number of hours for a PPL is 45 with most people taking around 60 to pass plus 9 written exams.
Commercial PL is 200 hours which includes 150 pilot in command - most people now do the ATPL additional exams when qualifying for cpl and have them frozen.

9 written exams?  Wow. Are there a bunch of specific subjects? In the US, it used to be I think a 60 question test out of a bank of 600 or 700 question types, many of which you had to calculate the answer, but some which just required memorization. Similar for an Instrument rating.  I went thru All the questions and made sure I could either do the math, knew the answer, and knew where to find the answer if I needed more detail behind it (such as the FAR, the AIM, etc.)


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What are the differences between porpoise; bounced; and nose-pointed-down landings?
I have read some articles, and to tell the truth, I could not clearly see the differences. I would like to know if there are differences or not.

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text:
I received a 1st Class medical certificate in May 2005. Do I qualify for BasicMed?
One of the requirements for BasicMed is:

Comply with the general BasicMed requirements (possess a U.S. driver's license, have held a medical after July 14, 2006).

I received a 1st class medical certificate in May of 2005. I was under the age of 40, so it would have been valid for 12 months, expiring in May 2006 (i.e., just before the BasicMed cutoff).
That said, it would have still been valid for an additional 24 calendar months (i.e., until May 2008, well into the BasicMed era) as a 3rd class medical. Am I correct in my understanding that this qualifies me for BasicMed?
Thank you.

As Stephen said, you are good as long as your Med cert was not revoked, suspended, or declined upon renewal. A medical of any type is the requirement. That being said, you had a first class certificate with third class privileges.

Your first-class medical certificate issued in May 2005 granted, since you were under 40 at the time:

First class privileges until May 31, 2006
Second class privileges until May 31, 2006
Third-class privileges until May 31, 2010

Since that last date is after July 14, 2006, then assuming it expired valid and you have not applied for another medical certificate since, you would qualify for BasicMed.

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text:
What does "square the base" mean?
I was flying the other day and heard tower say to another aircraft, "square the base". What does it mean, and when might a controller say this?

" Squaring the base" or "squaring the base to final" is a non-standard instruction used by the controller asking the pilot to fly the base leg until the correct point where he can make a proper 90° turn onto final.

This being the correct normal procedure in the pattern, he is simply asking the pilot not to cut the corner. This is usually done for spacing to allow enough time for the traffic ahead to clear the runway.
If the controller needs the pilot to expedite his landing he may give the opposite instruction, something like, "proceed to the numbers" or "straight to the numbers." This indicates that the controller wants them to cut the corner and take the most direct route to the threshold making time for traffic following.

Since these instructions are non-standard the wording may vary between different controllers.

The other two answers correctly describe the situation where an aircraft is in the local pattern already. But there is another situation where controllers might tell an aircraft to "square your base to final:" when the aircraft is inbound to the airport and in a position to make a modified straight-in, and the controller does not want them to. Again, this is a delaying maneuver.

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How to get the correct speed/power on downwind?
(Note: in this example I'm taking speeds from a Cessna 172)
I was taught that on downwind, you fly at pattern altitude at a normal power setting until you beam the numbers, at which you reduce power (to 1800 RPM.. ish) and start your descent. I was also told that the speed of each leg of the descent should be 80 (downwind), 70 (crosswind), and 60 (on final), and you add 10° of flaps each leg.
I'm running into two related problems:

On downwind, my airspeed can be 100-100 knots. This means I float for awhile at pattern altitude after beaming the numbers to get my airspeed down before starting the descent. I can't extend flaps until I'm under 80 knots and in the white arc.
My goal is not to add power after I've taken it out. Idea is to control the landing enough that I can still make the runway during an engine out. If I reduce the power a lot to hit 80 knots, I end up having to add a bunch of power on final to make the runway. If I keep the nose high and drop airspeed after beaming the numbers, I end up floating too far away before starting my descent, causing me to fly a larger pattern, and the need to add power to make the runway.

How do I control the speed and power setting to have a graceful pattern and smooth power setting while landing?

I have used 100 mph (not knots), 10 flaps, and carb heat on at midfield since my C150 days. 90 with 20 flaps on base, 80 with 30 flaps on final. 800 feet AGL about a mile from midfield works well, reducing power more as I certain to make the runway. I fly a Cardinal now, the same speeds work. Too fast and the plane really floats.

Part of your problem is being "behind the airplane", which is something that takes experience and practice to overcome, and part is it doesn't sound like you are being taught to fly very well.
It's key to understand the use of trim as your "hands free" speed control. Airplanes pitch to speed, and use power to determine climb, level descent at that speed (if you learn on gliders, this is easy because there's no engine to complicate things).  For the pilot, trim determines the speed the airplane will seek when you aren't holding the controls, and the objective is to exploit this feature.
In general you should always be seeking a condition where the airplane maintains your speed without you having to continuously hold forward and backward force on the wheel.  If you do that you invariably relax the force and your speed drifts.
So if you're going 100 and want to slow to 80 without climbing, you have to reduce power while you pitch to the speed, following up with trim once you're there.  Before you start doing circuits/patterns, you should be trained to do this automatically during air work.
Once you have that automated you will be making power changes, pitch and trim-to-hands-off on speed pretty much in a single smooth action, all the time without thinking, and now your head is free to think beyond those basic actions and will be able to anticipate when to make changes in advance, and you'll have "caught up" to the airplane.
The other thing to keep in mind is with tractor airplanes with the tail in the slipstream, there are small changes to trim speed with power changes due to the slipstream "blowing" harder or less hard on the tail.
If you are on final at 70kt and get low and add a lot of power, your trim speed will go down a bit and the airplane will slow to say 67kt if left hands free.  If the power application is temporary, you normally leave the trim alone and push to keep the nose from coming up, but if the power application is more long term, you will need to add a touch of ND trim to correct trim speed to 70kt.  Vice versa for power reductions.

I spend most of my flying time in C172s of various models as well as 152s, PA-28s and the like. In most C172s you can extend 10° of flap at 100kts, or even 110kts in some models. The white arc is usually for 20° of flap and above and that's 85kts not 80kts, but you should check the POH to be sure or it may be written on the flap handle placard. 10° of flap will certainly help, but it's more your technique that seems to be the issue here.
Your goal to not add power after you've taken it out is what is the biggest reason for your float, and isn't really constructive. It's normal to reduce throttle to meet a particular airspeed and then throttle up again, if you don't you are relying solely on drag to slow you down, which as you have discovered takes time. Cessnas are draggy beasts because of their low wing loading, wing struts and big rivets, so you can kinda get away with it, but if you tried that in a PA-28 you'd float much, much farther as it is less draggy, so it's not a good habit to get into as you'll be carrying too much extra speed throughout the approach.
You're never going to hit on the perfect throttle setting that will carry you around the pattern and touchdown at just the right point, there are too many variables to factor in like wind direction, wind speed, rising or falling air, etc. Fixing your throttle forces you to fly a specific pattern for the specific conditions, which won't be the same pattern as everyone else, and it will be different every time. There's no benefit to doing it.
The moral of the story is don't be afraid to use the throttle as necessary to control your energy, that's what it's for. When you need to reduce speed throttle back more, then increase again when you get to your target airspeed. In the approach make throttle adjustments required to maintain the descent rate you need, if you start to get a bit low add some, if you get to high pull it, and practice practice practice.
Don't worry about engine failure in the pattern either, if your engine quits you most likely have enough energy to make the field, just clean up and fly your best glide speed. Try it with your instructor: throttle back to idle at downwind and fly a curved approach onto the runway, you'd be surprised how much energy you have at the end.

according to this C172 POH, the maximum flap speed is 85 knots https://wayman.net/files/Cessna-172N-POH.pdf

Like I said, not all models are the same.


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Where can the airspace boundary coordinates for Fayetteville TRACON be found?
I would like a map depicting the airspace owned by Fayetteville TRACON that includes lat/long coordinates (i.e. not just a cartoon-y outline with no information). Ideally, I'd like to find a site whereby I can look up the airspace map for any ATC facility, but, for the moment, I'd like Fayetteville.
Any thoughts?

And I'm guessing you would like to know MVAs and frequencies. I'd love to be able to find the same thing. It seems like it would be very valuable for SA, instead of slowly compiling mental maps from experience.

I will second @StephenS's image as the best you're likely to find with minimal effort. In fact there are a few of these images available if you do an image search for "FAA STARS TAMR" and I've included all of them at the bottom of this answer.
Real answer
If you need the specific boundaries you can submit a FOIA request. If you're a private citizen who wants the information for non-commercial use this should be free, but it may not be. Here is the FOIA form for the Air Traffic Organization FOIA Coordinator for the Eastern Service Area, which should be who you want. I would probably say you're requesting "A document showing the boundaries and coordinates of Fayetteville ATCT center-delegated airspace" and that you think it would be found in the FAY SOP and/or in the LOA FAY has with Washington ARTCC.
Alternatively, if you have a controller friend who's willing to do you a favor you could ask them to pull up the SOP/LOA for FAY from the FAA intranet next time they're at work. All facilities should have their SOPs and LOAs stored on a system that can be accessed at loa.faa.gov from behind the general firewall. This is probably against policy though, so they might not be willing to do it for you.
Unofficial but likely workable answer
The VATSIM community strives for realism, and from time-to-time submits FOIA requests to the FAA to form the basis for their SOPs and maps. The Virtual Washington ARTCC website includes a page of downloadable "facility files" that you can open in a virtual radar client in order to see the airspace boundary (by enabling the "VIDMAP" map). I have no reason to doubt this map's accuracy, as it looks quite detailed and appears to match the boundaries shown in the maps below, but there is no guarantee it is accurate or current.
To find the geographical coordinate of any given point on the map, you can type F7,D,* and then click on the point. This shows the coordinate in what appears to be a hybrid Degrees Minutes.TenthsHundredths format. These coordinates must be defined somewhere in the downloaded "facility file" but I do not see a way to extract them on their own; you could get in touch with the VATSIM community to ask for the originals.
This method would probably work for any facility in the country, and although there is no guarantee of accuracy, airspace boundaries do not change often at all. It may be more time-effective to ask the various VATSIM communities for access to their FOIAed documents than to duplicate their effort by asking the FAA for each individual facility.
Interesting graphical history
An older map, still shows ARTS facilities. No date. FMH and ACK still separate. NMM is an FAA facility. JST not shown. Original

Map from September 2013. FMH and ACK still separate. NMM is an FAA facility. JST not shown. Original, 1620x1080. This is the highest-quality map of the bunch.

Map from September 2014. Very poor quality, hard to tell the differences from 2013. FMH and ACK still separate. NMM is an FAA facility. JST not shown. Original

StephenS's undated map. FMH and ACK have merged to create K90. NMM is an FAA facility. JST not shown.

Map from July 2018. This version shows ARTCC boundaries as well! K90 has been absorbed by A90. NMM is now run by the DOD. JST is a wholly new approach facility running airspace delegated by ZOB, located between PIT and MDT. The facility covering Edwards AFB and the R-2508 complex is now designated E10, "High Desert TRACON," instead of EDW. Also shown are the then-in-progress airspace consolidations (Section 804 or otherwise): MFR to EUG, YKM to PSC, MSO to GEG, RNO to SCT, BZM to BOI, GJT and PUB to D01, SJT to MAF, FYV to FSM, COU to SGF, LYH to ROA. Original

Map from June 2019. STARS is almost ubiquitous, with only two ARTS 2E and four ARTS 1E facilities left that I can see. Transfers of YKM to PSC, COU to SGF, and LYH to ROA are complete (as are the others from 2018, I think, but the arrows are still drawn because the airspace is not contiguous). MKG, MBS, LAN, and FNT have been combined into a super-TRACON at AZO now known as "Great Lakes Approach." Original

As of 2021, I believe there are no remaining ARTS facilities; all facilities are using some flavor of STARS. E10 is now JCF, "Joshua CCF." MFD and CAK have both been consolidated to CLE. PSC is being consolidated to GEG, taking YKM airspace with it. PIA and SPI are being consolidated to T75. HUF is being consolidated to IND. ZSU's Center functions are going to ZMA and the approach is being consolidated to RSW. FLO and MYR are being consolidated to CHS. There are probably some more I'm not remembering.

Great improvement on my answer!

To be honest, I didn't see that the highest voted answer was yours, but yours is also a non-answer as it misses coordinates that the OP asked for. Good encyclopaedic knowledge but not an answer.

A very good point @Stelios. Thinking on the question more, I came up with a possibly workable solution that will allow OP to extract coordinates that are—probably—broadly correct. It should be good enough for unofficial use (e.g. a quick "who should I call" when airborne, but not "who is responsible for the land over my house right on the boundary").

@randomhead chat?

The closest thing I could find was MVA and MIA Charts from FAA web site. The data format is in AIXM (XML) but I am not sure if this will cover you as I haven't tried reading any of the AIXM files. By looking into the PDF that provides the "cartoon-y" preview, it seems that the data are only that: MVA and MIA. If you need anything more than that, then I guess you will need to fuse data from other sources as well.
For example, this is what the Fayetteville PDF that you were asking for looks like:

The MVA map for a facility will generally go out to 60 NM (or more, as needed) regardless of the actual configuration of the airspace. Nothing shown on this map has any relation to boundaries of the airspace controlled by Fayetteville Approach.

@randomhead And you think that this is a reason for downvoting? Anyway I guess I should say "thank you" as usually people downvote without comment. I said the closest I could find. If you have any better source than that then please by all means add an answer.

Yes, sorry. There is no relation between this MVA map and OP's question (though JWalters may appreciate the information). I do not know of a better source besides the nationwide maps posted in my answer, unfortunately.

That's fine, have it your way. :)

I’ve been looking for years myself, and this is the best facility map I’ve been able to find so far, shared in a private forum by some ATC folks:

I know this is exactly the kind of “cartoon-y” outline that you don’t want, and I expect to be downvoted for it, but maybe others will better understand what you are looking for: a map of airspace ownership rather than the typical maps of airspace class.

Skyvector to the rescue!
You will find APP/DEP procedures, maps, frequencies, the whole nine yards!
EDIT:
Because it was stated in the comments, that SkyVector information is incomplete:

the charts show Fayetteville TMA and all instructions
The boundaries will depend on VFR, IFR and altitude, so you need to look at the charts
With the appropriate software to read it, you can download the AIXM files from the FAA, they hold the exact coordinates
the chart tells you, you are in Washington ARTCC
It will also tell you to contact FAY when you are 20NM out
the general information tells you the frequencies for APP/DEP

Skyvector has all the information for Fayetteville airport itself, but it doesn't show the airspace controlled by Fayetteville TRACON

Edited the answer to explain, what can be found in the chart; also explained where to find exact coordinates


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What to do when pneumatic air cycle kit stops working mid-flight on Boeing 737-800?
If you are flying a B738 at FL390, and one PACK (pneumatic air cycle kit) becomes inoperable, do you have to descend to FL250? If so, do you need to divert for fuel?

Please tell me this wasn't posted from the flight deck...

Different airlines may have different policies, but I think what my airline uses is probably pretty standard in this regard: no, you can continue at FL 390.
The limitation of not exceeding FL 250 on one pack comes from the MEL, which is a pre-takeoff document.  If the pack is known to be inoperative before takeoff, then the flight has to be planned at an altitude no greater than FL250, which means that the fuel planning has to account for the burn rate at the lower altitude.  However, when a system fails after you are airborne, the controlling document is NOT the MEL, but the QRH (i.e. your non-normal checklist for pack failure).  The QRH from Boeing does NOT direct you to descent to FL 250 for a single failed pack, for exactly the reason you allude to in the question -- you might very possibly have to divert due to the higher-than-planned fuel burn.
So in the case of a pack failure at FL 390, you can continue that flight at FL 390 as planned, but all subsequent flights until the pack is repaired have to be conducted at or below FL 250.
Some airlines may have a different policy, but that's the basic answer from Boeing's documents and philosophy.  Also, fuel permitting, some pilots might descend from FL390 to something a bit lower if they thought that the remaining pack might have an issue, just to provide a bit of cushion in case it does decide to stop working.  Packs fail rarely enough, though, that the risk of the second one failing on the same flight is pretty remote -- which is probably why Boeing is okay with continuing at the high altitude for the one flight, even though if you'll have to fly several more flights before getting repairs, they want the risk minimized for the others.  Risk management.

Would the failure of one PACK effect my cabin altitude, or could I maintain max differential with one PACK?

@ArthurCarson One pack can maintain cabin pressure just fine at any altitude.


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What is the formula for estimating the maximum stationary thrust of a rotor as function of its diameter?
I am new! New to this forum and new to aviation (i normally deal with statics) so thanks in advance for beeing patient with me.
Recently i was trying to figure out how much weight a rotor can lift as a function of the rotor diameter.
Therefore I came across this formula.
$$
T_{rotor} =(0.5*P^2*η_{rotor}^2*η_{el}^2*π*d_{rotor}^2*ρ_{Air})^{1/3}
$$
This brings me already quite close to my goal as I now have $ Thrust = f(P^2, d^2)$. Now I tried to relate the engine power to the rotor diameter by using :
$
P=T * {rpm}$  with $ T=I *α=(0.5* m*r^2)*v_{sound}/r $  and $ {rpm}=v_{sound}/(\pi*d)$
Which leads me to
$$
P(m)=(v_{sound}^2/(4*π))*m
$$

From this calculation a few questions arise:

Do you think this is a good estimate (within +-15%)?
Is there a better formula to estimate $I_{rotor}$ than using $I_{zylinder}$?
Is there any formula to estimate $ m_{rotor} = f(d_{rotor})  $

I want to add  that this estimate is for a rough feasability study and not to design a rotor or aircraft. I also know that several of the values in this formulas are a function of altitude and aircraft velocity. Please dont take this into account. At the moment I am only interested in a stationary solution.
Thanks for your help!

Please don't forget the root, which makes thrust proportional to d$^⅔$ only, less than linear.

You lost me at the P = T * rpm. Is this T for torque? What is I and which $\alpha$ are you using, angle of attack?

The $T = I \cdot \alpha$ is the formula for determining the torque as a function of the angular acceleration, which you can also see here. This however is not the right formula to use, as it completely neglects all air drag, and only accounts for inertia. What would happen if we have a constant rpm, and thus $\alpha = 0$? We need 0 torque to drive the rotor? OP, please check where the formula comes from, and its applicability

No the equation in your question is not useable. However there are tabulations of existing helicopters that provide a better method.
Maximum stationary thrust as a function of the rotor diameter. What you are looking for is related to the disk loading of a helicopter: when in hover, the rotor thrust equals weight. Heavier helicopters must unfortunately use higher disk loading, a feature dictated by the Square-Cube law. From Helicopter Aerodynamics by J. Gordon Leishman:

This is a direct relation between blade radius and max gross weight, no need to introduce the installed power etc into it. Note that the trend line is proportional to $W^{1/3}$.
When in hover at max gross weight, there is some more lift in reserve. How much depends on the disk loading and the air density. In another question we came to an estimation of twice the max gross weight at sea level valid for the disk loading of the Prouty example helicopter = 7.1 lb/ft$^2$ / rotor radius of 30 ft / max gross weight of 20,000 lb. For heavier helicopters the disk loading is higher, and this lift reserve reduces with disk loading and gross weight.

The above is a digitised plot of the line in Leishmans fig 6.3 in metric units, weight in N and radius in m. Lift in the hover is proportional to the square of the rotor radius - which makes sense, proportional to the rotor disk area as in equation:
$$T = C_T \cdot \rho \cdot A \cdot {V_{tip}}^2$$
As the rotor radius gets larger it turns slower, to prevent the blade tip from exceeding the critical Mach number.

Thanks a lot for your expalantions. The graphs are very helpful and exactly what i am looking for. The lower graph is from Leishmans "Principles of Helicopter Aerodynamics"?

The upper graph was used as a baseline. It is on a logarithmic scale, I digitised it, converted to metric and plotted on a linear scale.

I see :) Thanks again

The dimensional approach is simple... It can be safely assumed that the lift $L$ is a function of the input power $P$, the diameter $D$ of the rotor and the air density $\rho$.
Thus, $L = f(P,D,\rho)$
where $f$ is a function to be determined.
From dimensional analysis, the lift $L$ can be easily derived:
The variables are Lift $L$, dimensions $MLT^{–2}$; Power $P$, dimensions  $ML^2T^{–3}$; Rotor diameter $D$, dimensions $L$ and air density $\rho$, dimensions $ML^{–3}$
The variables form a non-dimensional product $k$
$k = L^a\cdot P^b\cdot D^c\cdot \rho^d$  where $a,b,c,d$ are numbers to be determined.
Let’s form now a parallel product $k^*$ with the dimensions:
$k^* = (MLT^{–2})^a  (ML^2T^{–3})^b  (L)^c (ML^{–3})^d$
Clearly, $k^* = M^0 L^0 T^0$... We now take the exponents for each dimension:
$a  + b + d = 0 \\
a + 2b + c – 3d = 0 \\
–2a – 3b = 0$
We make $a = 1$, since $L$ is the variable we’re going to solve for.
$b = –2/3 \\
d = –1/3 \\
c = –2/3$
Then,
$k = L^a\cdot P^b\cdot D^c\cdot \rho^d \rightarrow  k = L\cdot P^{–2/3}\cdot D^{–2/3}\cdot \rho^{–1/3}$
Solving for $L$
$L = k\cdot P^{2/3}\cdot D^{2/3}\cdot \rho^{1/3}$
where $k$ is a constant to be determined...

How is lift proportional to $\rho^{1/3}$? In the equation $T = C_T \cdot \rho \cdot A \cdot (\Omega \cdot R)^2$ the rotor thrust is proportional to $\rho^1$

@Koyovis. The dimensional derivation is correct. Hence, rho must have the exponent 1/3...

@Koyovis In https://en.wikipedia.org/wiki/Disk_loading#Momentum_theory you'll find an expression for the power required in hover as a function of the thrust, disk area, and air density. Solving that expression for thrust, you'll see that rho appears with the exponent 1/3...

For the power, yes. But we're trying to find thrust as a function of blade radius.

@Koyovis  If you solve that expression for thrust, you'll find that rho has the exponent 1/3, exactly as when derived by the dimensional method.


text:
What measurement units are used in Boeing FDR readouts?
I am working with FDR readout data and I am trying to find good resources about measurement units for those logs. The data seems to be a mix of SI and non-SI units and it can be quite difficult to work with data if you don't have correct units.
The data comes from Boeing 757, 767 and 737MAX aircraft but I am not sure what type the FDR equipment is installed (will find out at some point).
Does anyone have a good resource on this?
I am using this data to create graphs and measurements in Elasticsearch and Kibana, focusing on fuel efficiency. It is quite interesting to see how fuel flow is different between engines and how altitude affects fuel consumption.

Have you tried referring to ARINC Characteristic 747-3, Flight Data Recorder?  It should have the relevant information, though you may also need a copy of ARINC 429 to understand individual data parameters.

Whoever supplied the data should be able to supply what’s called a data frame description which explains how to translate the raw data into engineering units. It can be different across tailsigns even on the same type.

@Gerry, the spec of the FDR does not give the order of the recorded parameters except for the first words that concern the airplane identification. In arinc 429 the label gives the parameters, on the FDR we have only 12 bits words, the parameters order is not mandatorily  the same

@Cpt Reynolds, not necessarily, the DFR data, are similar to QAR data, some maintenance engineers might deliver recorded QAR data, without knowing their interpretation

@user40476 Of course. The operator should be able to acquire and pass on the description though. It’s not necessarily listed in the AMM, by the way - none of my airline’s are.

@Cpt Reynolds every technical service of the operator has this because they follow repetitively some of these parameters on the QAR, the listing is the same as on the FDR. In AMM ATA 31 these are normally available. Otherwise you can’t make a useful use of the QAR.

@user40476 My fleets‘ DFDR frames are very different from QAR frames though. DFDR is much less extensive.

@user40476 my Airbus AMMs have those frame definitions, at least for the modern fleets, the (older) Boeing ones don’t.

According to the provisions in ICAO Annex 6 - Operation of Aircraft, Vol 1 and Vol. III, a Type I FDR shall record the parameters required to determine accurately the aeroplane flight path, speed, attitude, engine power, configuration and operation. Types II and IIA FDRs shall record the parameters required to determine accurately the aeroplane flight path, speed, attitude, engine power and configuration of lift and drag devices.
Therefore the listing word by word is not defined by the authorities
So
As a start, but not only, it depends on the age of the aircraft, for instance early 737 had 64 words of 12 bits, most of these words have the first 2 bits for binary states(open, closed, selected on or selected off, etc) the remaining bits are for an analog value expressed binary, such as pressure, speed, vario, etc. Some other words are fully for states conditions, that is every bit of the 12 bits of the word indicates a state.
To the opposite of early 737 late 737s have 256 words,
So it doesn’t depend on the type of FDR, but on the specific model of aircraft, the type of FDR is just a consequence; 2 FDRs recording the same number of words won’t have the same words definitions
But more than that:
The FDR will record what it receives from a computer that centralizes all the data and that manages the data into 12 bits words. The recorded data depends on the chronology of received words. This chronology doesn’t depend on the FDR but on the emitting computer that sends the data to the FDR
But also
It depends on the specific options of the aircraft, that’s why every aircraft has its own listing, the investigation center will get this data either from the aircraft manufacturer or from the operator, because the data is also available in the specific maintenance manual of the aircraft.
So unhappily  you have to refer to the maintenance manual of what, of the specific aircraft
Now a hint: if you find in the nature an FDR, how to decode it if you don’t know ahead to what aircraft it belongs?

Externally it has a serial number that will normally allow the required traceability
While reading the data frames the identification of the aircraft is recorded on the first words

Is this a general answer, may be yes. Am I giving the parameters of every recorded word, the answer is no; Am I giving the corresponding units? The answer is no; However I am telling where to find these, that is the specific maintenance  manual of that specific aircraft. Had I to refrain from answering? May be no. Since 1 year, not to give a general answer nobody has answered.  Nevertheless hope this has been helpful.


text:
What causes this error on the Collins 60A ADF system?
We've got a BAE Jetstream 32 equipped with a dual Collins 60A ADF system, and the co-pilot's side control head is:

displaying "FLAG 10" when we press the TEST button; We looked up the error code, but the only information we got is that the code corresponds to "ADF not locked in ADF mode" with no rectification. This is the first error of this type we've seen.
would not function for the last flight crew that flew it.

We tried replacing the controller, the signal adapter and the receiver. We've been banging our heads against this for hours. Anyone seen a similar failure, and know what we've been doing wrong?

Hi 3433, welcome to Aviation!  Although I think your question is well written and on-topic, I have serious doubts that it will accumulate good answers simply because of how specific the circumstances are.  Hopefully, I'm wrong :)

I'm voting to close this question as off-topic because it is about avionics equipment support, which should be directed to the manufacturer.

Since the problem didn't go away when swapping the controller or the receiver, I'd rule them out as culprits. The message indicates that it is setting ADF mode, but it isn't locked.  All of that tells me the issue is with the loop portion of the antenna or its cabling/connections.  I'd check the cable connectors and ring out the cables.  Any impedance mismatch between the loop cables could cause the issue.  If nothing shows there, then try swapping the antenna.

Very much an opportunity to contact Collins. They'd be able to get you the most accurate answer much more quickly than asking the world in general. I'd imagine that they'll also have a solution (or at least detailed trouble shooting steps) at hand.


text:
What is the difference between Hobbs Time and Tach Time?
Over in this answer there's a description of Hobbs Time versus Tach Time, and how the Hobbs counts hours while the tach time is equivalent to "hours at cruise RPM".
How do these two "clocks" work, and what do these numbers mean in practical terms for flying and maintaining an aircraft?

Hobbs Time
In most planes, the Hobbs clock is started and stopped based on an oil pressure switch, so it starts when the engine starts, and stops when the engine is shut-down. While it's running, it just ticks off a tenth of an hour every 6 minutes, based on "regular wall clock time". So a tenth of idling on the ramp is the same as a tenth at cruise.
Tach Time
The tach clock isn't really a clock at all, it doesn't actually measure time, it really measures engine revolutions. But it's calibrated such that a tenth of an hour of tach time is clicked off when the engine is at cruise RPM for 6 minutes. In other words, if the plane is at cruise RPM, the tach clock will be clicking off tenths of an hour at the same rate as the Hobbs clock, and the same as the watch on your wrist. But if the engine is idling at an RPM speed that's half of what cruise RPM is, then the tach clock will be running at half the speed of the Hobbs clock.
Relation
So, for the tach clock, less "time" is clocked when the plane is idling on the ramp, or flying at low RPM. For short flights (where ramp idling time is a significant percentage of total time), and flights where you're doing a lot of pattern work (and thus operating at low RPM), tach time will be significantly less than Hobbs time.
Maintenance
When an engine is replaced or overhauled, that engine is considered to be "zero time". Whether they actually reset the tach gauge to 0 when the engine is overhauled, or if there's a way to put a time on a brand new tach or Hobbs meter when the old one dies and is replaced, I dunno, but in general, I'd assume that the aircraft's engine and airframe log books are really the official recording of the progression of airframe/engine times, so I don't know that it's particularly important whether the tach is set to the engine's time, or if it's really just used as an incremental meter.

AOPA has a nice (and long) article about this.

"When an engine is replaced or overhauled, that engine is considered to be "zero time"."
This is not true. Only certain overhaulers can zero-time an engine. And to do so, the overhaul quality must be to certain exacting standards. For example, a top overhaul (usually just changing one or more cylinders out for new or refurbished cylinders) is not a zero time overhaul.

In a real zero time overhaul, neither the Hobbs nor the tach revolution counter is reset to zero, although they can be if the owner prefers. A log book entry is made to record the time the engine is put back into service and engine is computed as time on the meter minus the return-to-service time.

Is a 2000 hour engine overhaul based on time measured on the Hobbs or on the tach meter? Same question for the the 50 and 100 hourly. I am asking because flight schools charge on Hobbs time which often entails long taxis and I'd like to work out what the real costs of operating the aircraft are.

So when you're running an engine at max power for takeoff/climb, the tach time will run faster than Hobbs time? Or is tach time really calibrated to max power, and even cruise would run slower than Hobbs? If it really is cruise power, which one? My POH lists three cruise RPM settings.

@StephenS Answer 1: yes; Answer 2: it is calibrated to cruise RPM, not max power; Answer 3: you've to find out in your POH which cruise RPM is calibrated to tach.


text:
How to ignore faulty instrument readings in glass cockpits?
When an instrument fails in the cockpit, it is better cover it with something, either a dollar bill or a gauge cover (if you happen to have one of those), so we won't accidentally process the information from the faulty reading. My instructor taught me to literally smash the gauge, so the status of that instrument is not in question.
This works well in cockpits with rounded gauges. Nowadays, more and more GA aircrafts are fitted with glass cockpits. Obviously I can't just smash the screen, or else everything will be gone! What are the steps that one can take to avoid reacting to the faulty reading?

Like in a steam gauge cockpit, you can put adhesive INOP stickers on parts of the glass panel. Stickers for the Garmin G1000 are available commercially, and I had to use them extensively for my instrument rating.
Keep in mind, though, that glass cockpit aviation systems will detect a faulty sensor automatically, and the faulty instrument will just appear X-ed out (like the picture on the INOP sticker) instead of showing wrong values.
But even multiple sensor source cross checks doesn't keep you safe from misinterpretation. See Birgenair 301 accident for example.

I suspect the "inop" stickers for the glass display are used more for simulating an inop indication, than for covering one, since the display itself should blank out anything that it sees as bad data.

authors: Елена Макарова


text:
Is it legal to begin pilot training on a jet?
Disregarding financial and difficulty concerns, would it be possible (legal) for someone to obtain a PPL license on a jet aircraft?
If it is possible, would there be any restrictions on the license on operating piston engine aircrafts?

EDIT: the linked question asks about EASA regulations. This question is about FAA regulations, thus, the answer in the linked question does not apply.

Turbines are a separate class, so yes, you would not be allowed to fly piston engines. You'd need to get an extra class rating for that. I don't think there are any restrictions on doing your training using turbines, except your wallet.

See also this question

The linked question basically asks the same thing, only regarding EASA instead of FAA. If someone would kindly amend the answer there, I would close this question.

Related

@falstro The FAA doesn't have a separate class for turbine vs. piston. The turbine requires a type rating, but it would all be Airplane - Multi Engine. Couldn't fly single-engine, but piston twin would be OK.

@NathanG it could be ASEL if its something like an L-39

@rbp Fair enough, sometimes I forget about single-engine jets. If you could accomplish the checkride in one of those, you'd have an ASEL that works with pistons too.

The answer is yes; and yes, restricted to same category and class.

How does one get a solo endorsement for a type rating?

Here it is in 61.31 (2) Have received training required by this part that is appropriate to the pilot certification level, aircraft category, class, and type rating (if a class or type rating is required) for the aircraft to be flown, and have received an endorsement for solo flight in that aircraft from an authorized instructor.

This is not duplicate! This is about FAA, the other about EASA.

In theory, it is perfectly legal to do your primary training in a jet.
It is becoming common in militaries to do initial training in turboprops.
http://www.airforce-technology.com/projects/t6b/
Managing such a turboprop aircraft is actually simpler than managing your typical piston aircraft. One button start. One lever engine control.
Maybe some day that will become a single engine jet.

There is nothing in the US regulations and no references that I can find that prohibits a pilot from learning to fly in a jet aircraft.  There are multiple systems on a jet aircraft that are not found in small GA aircraft and the same systems are more complex.  A lot of professional pilots who fly the same jet for a career don't fully understand the different systems on their jet.
The issue isn't with the FAA though; it is with the instructor and insurance companies.
I certainly would not agree, as a CFII, to train a new student pilot in a jet.  I personally don't want to take on the liability for the payment I would receive for my services.
Most insurance companies will not ensure a student pilot to learn to fly in a jet.


text:
How does compression ratio change, if at all, from sea level to higher altitudes?
As I understand it, compression ratio is the max pressure inside the engine divided by the ambient air pressure. This is for turbojets and turbofans.
Sea level pressure is about 100 kPa. An altitude of 10 km would have an ambient air pressure more like 26 kPa.
So you would think the compression ratio must drop 4x, but the thing is, does the turbine spin any faster at high altitudes to compensate?
So how does compression ratio change, if at all, from low to high altitudes?
Edit: Maybe I should have started with hard figures. What are typical compression ratios for turbojets and turbofans?

The ratio should not drop, the effective pressure will, but it is still taking X ambient pressure and compressing it by some ratio. Just like a piston engine that has for example 13:1 compression ratio, it takes 13 volume units and compresses it to 1 volume unit, whatever that volume unit is when the engine takes it in.

@RonBeyer So you're saying, if the ambient air drops 4x, the max engine pressure will also drop 4x? Does this also imply that the turbines are spinning at the same RPMs?

A jet engine "expert" will have to answer that, but as far as I understand the compression ratio does not change for a given RPM based on the ingested volume of air. The difference is that "compression ratio" on a turbine engine differs slightly from compression ratio on a piston engine in that a jet engine's overall compression ratio is the ratio of the pressure measured at the front and rear of the engine. This implies that the ratio does not change based on altitude or RPM.

Strictly speaking, compression ratio is the volume ratio. In jet engines, we use (and you are talking about) pressure ratio. But roughly speaking, compressor work is determined by that pressure ratio (together with fundamental air properties and temperature) and not absolute pressure. With altitude, the ratio and RPM (roughly) stay, while absolute values: pressure, fuel burn and thrust - fall.

The compression ratio of the turbo machinery will not change with altitude as long as the speed of the compressor does not change (excluding Reynolds number effects). This will lower the maximum pressure in parallel with the outside pressure.
However, to create the same lift at altitude, the aircraft has to fly faster. In 10 km, where the air density is roughly 1/4 of sea level density, the airplane has to fly twice as fast. Also, air temperature drops with altitude, so the flight Mach number increases even more. And this Mach number determines how much ram compression happens ahead of and in the intake. Flying fast will increase the intake pressure level, which partially compensates for the lower atmospheric pressure. Since the pressure rises with the square of the Mach number, fast airplanes have a clear advantage here.
Take the Concorde: Its Olympus 593 had a compression ratio of measly 12, but the precompression around the intake added another factor of 7 at Mach 2, so the total pressure ratio between the peak pressure in the engine and outside air was over 80! Admittedly, this air pressure was only 76 mbar at the cruising altitude of the Concorde, so the absolute peak pressure in the engine was a much less impressive 6 bar.
Typical compression ratios
To answer the question about typical compression ratios: This correlates strongly with the age of the design: The first operational turbojet, the Junkers Jumo 004 of 1943, had a compression ratio of just 3.2 using 7 compressor stages. The more recent Eurojet EJ200 of the Eurofighter achieves a compression ratio of around 26 with a similar size and weight using 8 compressed stages, but produces almost 7 times more thrust. The main difference is better aerodynamics.
The most recent civilian engines achieve a pressure ratio of around 50 using 15 compressor stages. They can afford to compress the air more because they try to heat and accelerate the air as little as necessary during the combustion process. Since the maximum heat inside the engine is limited by the materials used, a higher compression in military engines would leave less thermal margin for combustion heating. The higher nozzle velocities of supersonic-capable engines are best achieved with less compression and more combustion heating.
Here is a plot of the pressure ratio trends for commercial transport engines (Epstein, 1998)

Thanks again, but does the OPR also take into account any ram pressure at the beginning?

@DrZ214: No, that table uses the static value (engine on test stand).


text:
Do nose cones work well at high angles of attack?
On a lot of fighter jets, I see a heavily slanted intake, such as the F-15.

I always thought this is to help ingest air at high angles of attack. However, what about something like the MiG-21?

There's no slanted intake there. Yet on Wikipedia it does say, "Its G-limits were increased from +7Gs in initial variants to +8.5Gs in the latest variants." And it has a citation for it.
So my question is, do nose cones work well at high angles of attack? And if so, how?

No, they don't.
The slanted intake is slanted because the top part produces a compression shock wave that hits the lower intake lip so all of the compressed air is ingested and nothing is wasted. In order to do this reliably up to Mach 2.5 (where the Mach cone angle is 73.8° from the vertical), the whole intake needs to be slanted by those 73.8° (actually a bit less due to the intake wedge). In order to adjust the intake for different Mach numbers, one or both parts are adjustable, as shown in the F-14 example below.

Cross sections of the F-14 intake at subsonic, transsonic and supersonic speed. Note that the shocks of the supersonic example do not fit well with the intake geometry – the geometry is optimized for a much higher Mach number than shown. See here for a better example.
Here is (admitted a quite messy) cross section of the F-15 intake. The adjustable upper wedge is clearly visible (picture source):

In order to minimize losses, the upper intake uses adjustable ramps in order to force additional shocks so the compression happens over a sequence of weak, oblique shocks.
Regarding spike intakes: They were the lightest and simplest way to produce efficient supersonic intakes and were ill suited to large sideslip angles or angles of attack. Note that they were a characteristic of early supersonic flight when speed was the main objective and have since been replaced by ramp or even pitot intakes.

Interestingly, a high G maneuver may have lower AOA than a stall maneuver.  The MiG 21 spike inlet is 1950s vintage, also seen on the SR-71, used to solve the problem of slowing supersonic inlet air to subsonic flow that was then fed into the turbojet.
The MiG 21 was designed more for hit and run and is not as versatile as the F-15 Eagle, which suceeded it and it's F-104 Starfighter and F-4 Phantom contemporaries in the 1970s.
It is doubtful a spike inlet would be anywhere near as effective as the F-15s inlets during low speed, high AOA maneuvers, but neither would the rest of the plane.  It would be far better off to stay with its strengths.
The MiG 29 and Sukhoi Su 27, developed and put into sevice just after the F-15, feature similar air intakes, as does the fastest of them, the MiG 25.
In seems that the designers reasoned that the nose of the plane itself could be the "spike", placing the turbojet intakes on the side (further back) inside the shock wave "cone".
For subsonic high AOA maneuvering, the advantages of placing angled intakes on the side (or underneath) are obvious, and could lead too ... a better pitot tube design for GA aircraft.

"The MiG 29 and Sukhoi Su 27, developed and put into sevice just after the F-15, feature similar air intakes" - similar to what? "For subsonic high AOA maneuvering, the advantages of placing angled intakes on the side (or underneath) are obvious, and could lead too ... a better pitot tube design for GA aircraft." - not so obvious to everyone, and what do pitot tube designs have to do with the question?

"Similar to what?" The F-15.  "What do pitot tubes have to do with the question" Maintaining airflow at higher angles of attack.  No, I do not propose using pitot tubes as sources of thrust.

Pitot tube would be maintaining pressure at higher AOA with similar design, which would make it more accurate. (But now we must consider the benefits of erroneously low airspeed readings, which would prompt the pilot to reduce AOA sooner).


text:
Has there ever been a centrifugal turbine in an aircraft engine?
These days, most jet engines feature axial compressors and turbines. However, there are some older aircraft engines with centrifugal compressors, like the Rolls Royce Nene. But I've never heard of any engine with a centrifugal turbine (radial flow turbine).
Does such a thing exist? Has one ever been built, tested, and flown? I'm interested in turboprops, turbojets, turbofans, even very tiny ones for RC aircraft.
Edit: Okay a radial flow turbine will not produce much of a jet of thrust, so I guess the only possible engine for this would be a turboprop. Edit 2: Not necessarily, a centrifugal compressor can redirect air outwards to another path, then downwards into a centrifugal turbine, which redirects it back to axial direction after all.

I've only ever seen them in turbo chargers, and air cycle machines in air conditioning packs.  Even the itty bitty Jet Cat RC turbojets use an axial turbine.  I think they are just too inefficient for turbojet purposes, the compressor torque demands for a TC or ACM being much lower than a turbojet, but it'll be interesting to see if someone dredges something up.

I think you're misunderstanding how radial turbines work.  Centrifugal force works against gas flow in a radial turbine; gas is inducted at the periphery and moves toward the center.  This is more like the operation of a Peltier water turbine than that of a centifugal compressor.

@JohnK An impeller is the compressor portion -- though I usually see that used in pumps for liquids, it occasionally applies to gases, too (a fan is an impeller, whether airscrew type or squirrel cage, for instance).  You may be conflating with an "impulse turbine" which is the Peltier type I referenced above, also used in steam turbines where a de Laval nozzle blows on the moving blades.

Oops brain fart...

@ZeissIkon I might be misunderstanding something, but I reverted the edit and made my own. I thought centrifugal and radial flow would be synonymous here? If not, can you explain it more? I don't think I'm confusing the Peltier type turbine he made for a waterwheel. I envisioned turbine geometry very similar to the centrifugal compressor of a Nene. So it would have some axial and some radial flow (by that I mean flowing away from the axis, not flowing around in a circle like a waterwheel).

@JohnK I don't see anything wrong with your comment, can you clarify?

I called the turbine part an impeller which is another name for centrifugal compressor or pump (in the case of fluids). Just got names confused in my head.

@DrZ214 The geometry of a radial turbine is mirror image of a radial compressor -- see a common turbocharger for the easily found example.  However, in the compressor, air enters at the axis, is compressed by centrifugal motion, and exits at the periphery, where in the radial turbine, the hot gas enters at the periphery, does work on the rotor and against centrifugal force and exits at the axis.  Doing part of its work against centrifugal force automatically extracts a penalty that's not present in an axial flow turbine, which is why almost no jet engines were built with radial turbines.

The Heinkel Hes 3b, which powered the Heinkel He 178, had a radial turbine. This was the first operational jet engine to power an airplane.

Thanks, but now I'm looking for a good diagram of the engine and can't find one. Do you know where one is? I want to see how many times the exhaust is redirected to make a jet of thrust. With the turbine redirecting things radially, it should require at least 1 more change in direction.

I don't really have much more than what I linked. There's another image here: https://airandspace.si.edu/collection-objects/heinkel-von-ohain-hes-3b-turbojet-engine-reproduction/nasm_A19810039000

@DrZ214, the cut-out on the (linked) Wikipedia page is not that good, but good enough to show that the flow is inward. Basically reverse of that in the compressor.

@JanHudec Oh i think i get it now. The compressor redirects air upwards along some other path, then it goes downwards to the centrifugal turbine, which redirects it back to axial exit flow. So it is a jet of thrust after all. It's still strange tho because the compressor looks axial, not centrifugal.

It has an axial "inducer", followed by a centrifugal compressor.

@DrZ214, also google image search gives me link to https://www.valka.cz/15630-Vyvoj-druhovalecnych-proudovych-motoru-u-firmy-Heinkel, which is in Czech, but it has a cross-section diagram with the flow marked around mid-page. It confirms the turbine flow is inward.

@JanHudec Thank you, those are much better. What an interesting engine! I'm going to ask more about them and if they are actually less efficient or if it's just the greater diameter making higher nacelle drag.

I'm interested in turboprops, turbojets, turbofans, even very tiny ones for RC aircraft.

I don't know about any practical designs for aircraft that use a centrifugal turbine. That seems unlikely to me, given the history of development of turbine aircraft engines as compared to other turbine designs (especially the automotive turbocharger, which predates aircraft engines).
But there is a significant community of people dedicated to converting automotive turbochargers (with centrifugal turbines) into jet engines. My own perception of the results is that this constitutes mainly people who manage to get a turbocharger-based engine to run self-sustaining on a bench as a proof of concept and go no further, but there are claims of success in installing such engines on small vehicles, such as go-karts and model aircraft.
Are those claims justified? I can't say. There are a lot of people on the Internet claiming all kinds of outlandish things that have no basis in reality. Feel free to judge for yourself. :) Here are some examples:
Will a JET ENGINE made from a LOO roll holder WORK?
FIRING UP THE TURBOJET!
GR-1 Experimental Jet Engine
Jet Engine full power run Afterburner HX Monster Homemade jet engine
Jet and Turbine Owners (Proboards discussion web site)
Note that in none of these examples is the turbine engine purpose-built. These all involve taking the automotive design and attempting to adapt it for direct propulsion purposes.


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What turbine temp. would result from burning pure stoichiometrically?
I've heard that jet engine efficiency is limited by turbine temperatures---that is, the max temp. that the turbine blade alloy can withstand before weakening too much.
So jet engines are run fuel-lean. But they do achieve > 99% combustion of all fuel, so at least that's good. However, if we could burn stoichiometrically, then the engine could be smaller and lighter since it would need less air intake for the core.
So I want to know what is the max temperature that would result if you tried to burn pure stoichiometric?
BTW, to keep it simple, I'm asking about TIT (Turbine Inlet Temperature), which is the temperature of the gas right after combustion, right before it enters the first turbine stage. You can actually do complicated cooling on the blades to keep them less hot than that temperature somehow but I don't wanna get into that aspect.
Note, I'm interested in any typical large jet engine, like the PW6000, running at cruising conditions.
I found an example of actual TIT saying 1600 C: Mitsubishi site link. However, it was a gas turbine not jet engine, so I can't be sure if this is typical for jets too. What I want to know is the theoretical TIT if you could burn pure stoichiometric, to see what the difference is.

A gold and silver dealer once lamented to me about how his little torch could not melt a larger piece.  We then realized the silver was conducting the heat away faster than the torch was raising its temperature. Removing heat enables the metal to remain solid, even though the flame temperature is higher than than its melting point.  He found a larger torch melted the silver well.  Even in jets, the fuel burn quantity and stoichimetric ratio is important.  This is why we cannot "lean" at full throttle.

One may use the data I found for a previous answer for a PT-6 turboprop:

Ambient: 300K
Compressor discharge: 600K
Turbine inlet: 1200K
Exhaust: 800K

So, the combustor (between the compressor discharge and turbine inlet) adds 600K. Let's assume this happens at $\varphi=0.45%$ fuel equivalence ratio, which is equivalent to about 3% of fuel by mass. Since that's so low, we may also assume that all energy is put into heating the air (both the air used for combustion and the excess air for cooling the flow before the turbine). We start with a $\Delta T_c=1200K-600K = 600K$. Since a combustor is approximately isobaric, we can use the $c_p$ heat capacity for the reaction products, which is (for an ideal gas) not a function of temperature. We can thus simply calculate the stoichiometric temperature increase $$\Delta T_{s} = \frac{\Delta T_c}{\varphi} = \frac{600K}{0.45} = 1333K.$$ So the turbine inlet temperature is then $600K+1333K = 1933K.$ In reality, fuel heating (especially fuel evaporation) will represent a more sizeable chunk near stoichiometry, but I think it's safe to assume it's around the $1900K$ range.
Note however that the theoretical efficiency (ignoring the inevitable viscous losses from handling such a large flow of air) is determined solely by the pressure ratio of the compressor: $$\eta = 1-\left(\frac{P_1}{P_2}\right)^\frac{\gamma-1}{\gamma}.$$ So if TIT were not an issue, by enriching the mixture closer to stoichiometric, we do reduce the mass flow required through the engine (at constant power), so we proportionally reduce the viscous losses in the engine. If on the other hand viscous losses did not exist, for the most efficient design we would increase the compression ratio and lean the mixture even further to the point where the compressor discharge and turbine inlet temperature would be almost equal.


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What are the differences between FADEC and EEC systems?
Can anyone differentiate FADEC and EEC system in an aircraft Engines?
As I was working related to Engine controlling. I got confused of FADEC and EECs.
As per some of the doc. I read like EECs are a part of FADEC.

The EEC is the Engine Electronic Controller, the digital processing heart of the Full Authority Digital Electronic Controller. Kind of like the microprocessor in a digital computer. From The Jet Engine by Rolls Royce, 5th edition:

The EEC is dual redundant with all subs-systems such as sensors, cables etc duplicated, so that a single fail leaves the system fully operational. It is housed either in the airframe, or like in civil airliners on the engine, leaving it in need of protection of extreme circumstances:

Temperature - ice and tropical heat.
Electromagnetic radiation - lightning and airport radar
Engine vibration

The FADEC monitors inputs such as:

Shaft speeds
Engine temperatures
Oil pressures
Actuator positions
Power setting

and then sets fuel flow, variable stator vanes, and air bleed valves.

UTC's product description might help here:

The system consists of an electronic engine control, along with other accessories that work together to optimize fuel management and engine performance during takeoff, flight and landing.
In addition, we provide prognostics and health management electronics that provide more engine diagnostics and prognostics, which can alert the operator to needed maintenance actions before they become an expensive and time-consuming problem. Other technologies include advanced sensing systems

EEC or ECU is the main component of FADEC. It controls the engine actuation system depending upon the situation and the commands received from cockpit. It receives data from all the sensors, commands from cockpit. It processes the data and figures out what control commands need to be given to the actuation system and then execute them. While FADEC is an overarching system which includes EEC and some other components in it, such as sensors, health monitoring system etc. I think, a FADEC typically contains more than one EEC/ECU for redundancy.

EEC is a supervisory system which controls engine parameters and operation to prevent parameter exceedance (temperature, RPM, etc.),and comes into operation at certain engine speeds. It has a backup in case all the channels of EEC are lost.
FADEC is a full authority system, i.e. it controls engine operation and parameters at all speed regimes. It has no backup system.

Don't think this answers the stated question, which is what "answer" posts are expected to do. If you have a new question, please ask it in a new thread.

Hello solomon, welcome to aviation.stackexchange. Please don"t ask followup question in the answers, instead you can ask a new question.


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Does the wing to fuselage fittings of an airplane ever experience shear load?
Do wing attach fittings of semi-cantilevered plane (i.e. ultralights) ever get subjected to shear force? For example during roll, does the centrifugal force of the wings load the wing attach fittings with shear?

shear in which direction?

Span wise direction

In general, the answer is yes. The answer depends on the details of the fittings. Note that most realistic loadings are a combination of tension rsp. compression and shear. If - for example - the wing of your ultralight is held together by shear pins (note the name!) which are inserted in vertical (up-down) or horizontal (forward-backward) direction, they will transmit those centrifugal loads as shear from one wing bushing to the other.
The same goes for the transfer of lift forces inside the spar and - again, depending on the details - into the fuselage. The web of the spar is meant to carry the shear loads and those are transferred by ribs to the attachment points. Other designs use a front and rear spar which attach directly to the fuselage.

The picture shows the front spar attachment of the B-17 (source). Granted, this is not exactly an ultralight, but the same principles apply. At positions C, D and E it uses shear pins to transfer the lift loads into the fuselage bulkhead.


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Compression and tension members of a biplane wing
I get why the upper wing of a biplane is a compression member (because the flying wire is attached to it at an angle) but what I fail to understand is why the lower wing is the tension member of a truss of a biplane as explained here. So my question is why is the lower wing of a biplane referred to as a tension member of a struss?

It's not a tension member in that sense.  This is a pin jointed truss with flexible tenion-only diagonals.  The lower wing is a non-cantilevered beam, that is, supported at both ends, so it will bow up in the center under load with flight loads, and this applies a modest tension load at the root (as well as pulling the bottom of the interplane strut inboard, to the extent that deformation occurs in the main spar beam).   If the lower wing's spar had perfect rigidity and didn't bend at all, there would be no tension load at all at the wing root; it would be all vertical shear.
If you thought of the lower wing as a sheet of fabric, and imagine that the interplane strut at the outer end was rigid vertically, you'd have basically an upside down hammock, and when you lay in a hammock, the attachments are under tension (of course, the outer interplane struct not being rigid vertically, the hammock would collapse straight up - in the biplane's case the lower "hammock" is a semi-rigid length of lumber that only deflects slightly so the outer interplane strut doesn't have to be vertically fixed).  So the extent of any tension load at the root fitting for the lower wing, it's only to the extent that there is a hammock effect happening as the spar deforms.
To get the lower wing to work in tension as part of rigid truss system with the upper and lower wings integrated into it, the X of diagonal wires have to be replaced with rigid struts that can take compression.  The rigid strut running down from the upper root to lower tip would be in compression, sharing load with the other one in tension, and this would make the lower wing a tension member in the system.  But with tension-only flying wires, that doesn't happen.
Clear as mud?

If you push up on all the wingtips you'll tend to stretch the lower wing and compress the upper wing.  Just imagine what happens if you deform the structure by pushing up on all the wingtips, while pushing down on the fuselage.

If the top and bottom wings were joined by a shear web, so it was one big I beam, yes that would be the case,  But this is a pin jointed truss, where almost all of the load is in the diagonal tension member.  The bottom member is just going along for the ride, supported at the outer end by the interplane strut.


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What kind of waypoints/routes are used to prepare a flight plan in practice?
I have noticed that FAA provides data delivery service where both waypoints and ATS routes are available to download. By looking at the files, I realize that there are a variety of waypoints and routes. I really want to pick the particular type of waypoint, which are used for pilots to prepare a flight plan in reality. Could you please let me know which types of waypoints/routes are used in practice?
For reference, I am attaching the screenshot from which the types are categorized.
Types of Waypoint:

Types of ATS Routes:

What is this screenshot from?

Hi Michael, this is from a excel file and categorized by FAA.

All of them are used in practice—sometimes. Better question is given aircraft equipment and pilot certificates which can be used in a flight plan, i.e. what is required to actually use each type?

Hi Jan Hudec, thank you so much for your comment! I should have asked the better question as you suggested.

If you go to Skyvector.com and enter Departure and Destination airports, then select Routes, it will show you a preferred routing using waypoints that I think tries to use airways when possible.
If you change the altitude, different routes will show up.
In practice, for smaller planes anyway, I think most of us pick routes that will go as direct as possible, not going too far off shore, and not getting too close to Class B when possible. Depends on time of day too, Class B can a lot busier at some times than others.

Hi CrossRoads, that's good to know. So, for the small planes, I am guessing that you guys would think more the shortest time path than the fuel optimum path? Or maybe it doesn't matter? Please let me correct if I am wrong.

I think shortest time path would equal fuel optimum path, with shortest time adjusted to avoid long over water legs.  Flying down the east coast of the US, the shortest path V 139-268-308 takes you well off shore heading southeast of NYC. NYC airspace is quite large and goes up to 7000 ft, the times we've been VFR and westbound at 6500 ft, we've been cleared to go thru it, flying westward down Long Island, directly over JFK, a few miles over water to Colts Neck VFR, and continuing south from there.  I have heard of other folks doing it IFR and getting routed north and west of NYC, so it varies

Thanks for your information!

Routes were traditionally built using SIDs, airways and STARs, not individual waypoints (aka fixes).
From the departure airport, there will typically be multiple Standard Instrument Departure routes, each spreading out to several "transition" fixes. At the other end, there will be similar Standard Terminal Arrival Routes and transition fixes.
Then you find the best set of airways that lead from the chosen SID transition fix to the chosen STAR transition fix. For brevity, you only list specific fixes where you will change from one route to another.
Note that the shortest path in time (which should also require the least fuel) may not be the shortest in distance due to differences in winds aloft, and some potential routes may be eliminated entirely due to passing through severe weather.
The new "Free Flight" concept is touted as allowing every flight to make up its own route (at least between the transitions) out of seemingly random fixes, i.e. not using airways, but that is currently only available in relatively uncongested areas or altitudes rather than the norm.

Hi StephenS, thank you so much for your answer! It was really good for me to know. Would you mind if I ask you one quick follow-up question? So, did you mean that the shortest path in time does not guarantee the fuel-optimum path due to the wind aloft? Let's say we may have a fuel optimum path even if it's not the shortest path in time when departure and arrival points are given?

Of course experiences differ, but I have rarely built a route using SIDS or STARS.  Only on a handful of occasions where I know a SID will be assigned have I actually filed for one.  And generally once airborne with a tight inertial, on a long flight we would almost always ask for INS direct and most often get it.

@Sillykim The least time should also require the least fuel since planes usually cruise at a fixed fuel burn per hour. However, the least time may mean a longer distance over the ground with a tailwind than a shorter distance with a headwind.

@MichaelHall I'd still rather file a real route than risk an FRC on CD; I'll get the same shortcuts (if any) either way. EFBs make it easy to file routes that others have recently gotten approved fornothers with just a few taps, so why gamble?

Sorry, but what is an "FRC on CD"?  I agree it is not difficult to file for a SID, but if you would prefer an immediate turn on course then why not file for what you want and fly what they assign?  I am not understanding what you mean by "risk" in this case...

StephenS, it feels like that I now get your point. In summary, the least time always means the least fuel; however, the least time can be a longer distance with a tailwind than a shorter distance with a headwind. Please let me correct if I am wrong.

@MichaelHall Full Route Clearance (no "[and then] as filed") on Clearance Delivery, which is likely if you file direct. If you leave off just the SID, you'll get it anyways "and then as filed". Why not just file the route you'll probably get anyway? If shortcuts are available, you'll get them regardless of what you filed, so it doesn't hurt, but it saves time either way.

@Sillykim Correct.

@StephenS Thanks for the clarification!

Another way to see what routes are typically used for IFR flights in the US is to use the FlightAware IFR Route Analyzer. You can enter an origin and destination to see the routes from flight plans from the past 24 hours.
Of course, note the warnings:

For IFR flight planning, be certain to note altitude, type of aircraft and verify on terminal procedures that you are eligible for that SID/STAR/routing. [...] This data is for suggestion purposes only. Flights may not have been conducted as filed, aircraft type may be erroneous, or data may contain other errors. You must independently verify validity of data by evaluating traditional flight planning publications to be guaranteed of terrain separation, range (fuel capacity) for your aircraft, potential ADIZ/TFR penetration, and other issues that could be fatally hazardous to the health of you and/or your passengers.

So the utility of this information isn't great. As these routes have been worked out by professional dispatchers based on current conditions, equipment, restrictions, and every other flight planning consideration imaginable, the route you'd plan for your flight may be rather different than what an airline filed 12 hours ago.
But since it seems like you're interested in looking at real-world routes, this tool will allow you to see what those typically look like.

Hi Zach Lipton, thank you so much for letting me know this. It would be helpful to me.

@Sillykim FYI, to ping someone, use the @ then type the first couple of characters of their user name. A list of available options will come up and you can click on the one you're after. This will actually give the user notification that he's been pinged (as you just got) so she knows to come back and see what's up. Also, you don't have to ping the author of the Q or A - they're automatically notified, and there are no spaces in the names like @zachlipton (you can only ping 1 person per comment, so he won't get the notification).

@FreeMan Thanks for letting me know it! I feel like becoming more familiar with aviation.stackexchange.com :)

In real life the flight planning process starts with where you are, where you are going, and then you make decisions on routing based on considerations such as weather, terrain, alternate airfields, airspace, VFR vs IFR, etc.  Looking at the chart you will then choose appropriate waypoints along that route of flight based on the aircraft navigation equipment.  You don't generally start planning by making a blanket decision on what category of waypoint you would like to use.

Thanks Michael for your answer! Would you mind if I ask one follow-up question? When you are saying 'choose appropriate waypoints along the route', what kinds of waypoint would define the route? Let's say that the route is generated by only using RNAV waypoints? or it is possible to have a variety of waypoints such as RNAV and Reporting point in practice? For example, it seems to me that the real flight trajectory (from FlightAware) used three different types of waypoint, which are Waypoint, Reporting point, and NAVAID.

@Sillykim – Both high and low altitude routes have traditionally been defined by ground based Navaids such as VORs, but as GPS becomes ever more prevalent I think you will see more RNAV waypoints used.  Typically a “Victor route” (low) or “Jet route” (high) will hop from VOR to VOR.  For filing purposes you only need to list the route, and all waypoints along that route are included.  Rarely will such a route take you all the way to where you are going, (just like you need to get off the interstate at some point…) so other waypoints are added as necessary.  Do you have access to a chart?

ADDENDUM - It is certainly possible, and as I mentioned before, even preferable to plan your route using a variety of waypoint types on your route.  Compare it to driving:  You would never plan a trip using only cloverleaf interstate highway intersections, or decide to travel exclusively through flashing 4 way stops.  You would choose the most efficient route and intersections compatible with your vehicle type and planned destination.  Does this perspective help?

thank you so much for letting me know that I only need to list the route. If then, I may want to confirm with you that both RNAV and CONV are prevalent to define the routes over US. Please let me correct if I am wrong.

I'm not sure what CONV waypoints are, but RNAV is common.  I would recommend you check https://skyvector.com/ if you would like to see what kind of waypoints are used in the US.

CONV is presumably "conventional", meaning using only ground-based radio navaids (VOR, NDB, DNE, etc.), i.e. usable by non-RNAV aircraft.

Michael, I am so sorry for the confusion; however, I meant that both RNAV and CONV are a route. I have already checked SkyVector; well, actually, the original question arise from 'What kinds of waypoint are used in SkyVector?' This is because I believed that SkyVector is a reliable website. Do you know what kinds of waypoints are used in SkyVector by any chance? (based on the type that I attached)

@Sillykim - I am struggling to understand your confusion, and what it is you are really looking for.  Skyvector is a duplication of VFR charts, and the entire variety of waypoint types is represented.  Some are VORs, some are VOR intersections, and some are RNAV waypoints.  Are you trying to look at a specific waypoint and determine which of these it is?  Are you trying to actually plan a flight?  Is this idle curiosity about waypoint categories?  (i.e. what is the difference between 3 letters vs 5 letters?)  What is it you are actually trying to accomplish with the knowledge you seek?

You stated:  "I really want to pick the particular type of waypoint, which are used for pilots to prepare a flight plan in reality."  What does that really mean though?  What are you picking them for?  I explained that we use waypoints that we are capable of identifying along our intended route of flight.  What else are you looking for?

Does this help?:  https://aviation.stackexchange.com/questions/29982/what-are-those-5-character-alphanumeric-waypoints?rq=1

Michael, I am so sorry if it was unclear. Please let me clarify it step by step. 1) I believe that SkyVector provides reliable resources. As you know, there are a lot of waypoints and airways from the website. However, they are just information but do not provide type information. 2) I noticed that FAA also provides waypoint and route information. I downloaded the excel file and attached the screenshot for the type. 3) I wanted to know which types (defined in the file from FAA) of waypoint and route are used when SkyVector defined them on their website.

And I am telling you there are a lot of different types depicted.  Pilots may use any of them.


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Can anyone identify what/where this photo is of?

This is a photo by the Real Photograph Co. (Liverpool) No.684.
I think it may be a crashed WW1 Biplane (lots of the photos with it were WW1 biplanes).

The engine looks like it's 9-cylinder radial, and given the way the cylinders are seated on the body I suggest the engine is likely to be a Le Rhone 9J.
There's a fairing behind the pilots head, not large, which has come away revealing possibly access to the tank. That's a big clue. Further, the position of the fairing makes it likely a small single seater.
It's likely WW1 judging from the officer's uniform. Based on that, tentatively it could be an Airco DH5 or Nieuport 17.

@Party Ark Nice suggestion on the Le Rhone. I would however suggest that it is not  an Airco DH5, I base this on the fact that the DH5 utilized a spinner, which is not in evidence here. The Newport 17 also does not fit, due to the fact that it had a metal seat, while this aircraft has a wicker seat, in addition the Newport did not have a tank behind the seat. I would suggest that this may be a Sopwith Camel, I base this on the fact that the Camel has both a wicker seat and a tank behind the cockpit. I cannot however identify that specific tank design, so this is not an answer just a guess.

Not all Aircos had spinners (and it might have come off in the crash), but you're right the seat looks wrong. Camel is a good one; I'd expect the tappet rods in front of the cylinders to be visible, but it's not very clear. Certainly the tank position fits, and there is a suggestion of a wing support by the cockpit (left side as you look) which would be a v positive indicator. However, my reading is that there's a fairing behind the pilot's head that's come away - Vickers F.B.19 might be another contender, just to muddy the water. http://www.airwar.ru/image/idop/fww1/fb19/fb19-3.jpg

This could be a Sopwith Camel without its guns.  At least these details don't disagree:

cowling's shape and front opening
9-cylinder radial engine (tappett rods lost when crushed by the cowling)
8-bolt prop hub
wicker seat's weave spacing (many photos if you search "sopwith camel seat")
fuel tank's position and shape match that in the Haynes Manual
location of the remnants of the cabane struts.

Although some of these details are common to many aircraft of the period, it's noteworthy that this many details agree in one place.  A statistical argument may be the best one can do with what's been given.

It definitely looks like the nose of a WW1 or pre-WW2 aircraft. You can clearly see the pilot seat with the fuel tank behind it. In addition you can see the engine with  the rest of the two blade propeller.
I personally think that it is most likely a post WW1 but pre WW2 aircraft because it appears to have a NACA Cowling, like on this image from Wikipedia:

It was developed in 1927. As for the aircraft type, for me personally it's hard to tell what it could be.
Source: Wikipedia (https://en.wikipedia.org/wiki/NACA_cowling)


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Do two stroke engines for small aircraft suffer from degradation between overhauls?
Do two stroke engines for small aircraft suffer from degradation between overhauls?
For an automotive engines you can usually expect it to retain most of it's power between services for a long time until a specific failure occurs. During the time between overhauls on a small two stroke aircraft engine like a microlight, does the power available drop noticeably over time and increase after an overhaul/rebuild? Seeing as these only have a small power available to them to the begin with, as in 20-60hp, and this is in turn reduced with altitude, you would have to adjust your flight planning to compensate.
The other option is to have the TBO set to make sure things are changed before power loss becomes an issue, but this would necessarily involve changing out components while they still have usable life in them.

Don't overthink this stuff.
If the rings are good and there are no other abnormalities, there's no reason a 2 stroke shouldn't put out rated power over its service life.  And you would confirm this with a compression test periodically and a quick run at full throttle, while tied down, to check the static RPM.  With a fixed pitch prop, if the power output is down, the static RPM at full throttle will be down, assuming temperature and altitude are more or less the same each time.
Engines like the Rotax 582 were typically overhauled frequently by 4 stroke standards, something like 300 hours, due to potential fatigue on the crankshaft, not from performance degradation.  Possibly the newer versions are being run longer than that.  I've heard that some guys are running them to 500 or more.
So if you maintain the engine, don't allow it to overheat, do a compression test periodically, say every 25 or 50 hours along with a static RPM check at full throttle, you can assume the engine is making rated power and overhaul it only if it fails those tests or has reached the recommended rebuild interval.
And in your flying, don't put too much trust in those engines. It's not the power degradation from wear that'll get you, it'll be the thrown rod or seized piston at the worst possible time.  They are much more highly stressed than 4 stroke aircraft engines, which live a much easier direct-drive life and have really beefy components.  I would NEVER fly a 2 stroke beyond gliding distance of a landing spot.  The saving grace of ultralights is the fact that you can put them into very small spaces when the unreliable 2 stroke lets you down.

Agree with John K. In addition, 2-stroke engines are nowhere near as well-lubricated during operation as a similarly-sized 4-stroke, and by having a power stroke on every revolution, a 2-stroke engine running at, say, 4500RPM has to manage the heatup caused by twice the mass flow rate of fuel through it. The result: scored cylinder walls, burnt-through pistons, and pistons stuck in the bore. Talk to motorcycle mechanics about this and you'll get an earful!

Two-strokes are now seldom used in new ultralights, since they are environment-unfriendly, unreliable and require too frequent cleaning and overhauls. Rotax has discontinued the 447 and the 503; with only the 582 still in production.


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How are Cd and Cl calculated from Cp data?
Given pressure coefficient data for corresponding x/c (position along chord) values on a wing, I am looking to calculate coefficients of drag and lift. Here's what I have: b, MAC, S, sweep angles at LE & c/4, and Cp vs. x/c data for 6 different stations (span position given). Angle of attack is 0 degrees.
I understand that to calculate Cl, I can numerically integrate Cp with respect to x/c from 0 to 1. (ignoring skin friction [which, I know, is not best practice])
To calculate Cd (again ignoring skin friction), I believe I need to perform the same integration but with the Cp values being first multiplied by dz/dx inside the integrand, where z corresponds with the airfoil thickness.
My problem is that I do not have any information on the airfoil thickness. Any thoughts on approaching this? Is this problem possible? If it matters, I'm sourcing my equations from Anderson's Fundamentals of Flight, Ch. 1.

Without the local inclination of the airfoil surface you will not be able to achieve exact results for drag. You need to integrate just the component orthogonal to the flow direction at infinity for the lift coefficient (because it is defined that way) and parallel to that direction for the pressure part of the drag coefficient.
While it is OK to neglect friction for lift, it does contribute about half of total drag when the flow is attached, so it should not be neglected for calculating total drag.
To illustrate how important the local inclination is, here the c$_{\text p}$ plot of the Eppler 502 at a moderate angle of attack (3°):

And now the same thing, plotted with vectors. Arrows pointing away from the surface denote suction and vice versa.

Since the c$_{\text p}$ plot should use the projected length along the X-axis, this inclination effect is already considered when you integrate the pressure coefficient over chord. Treat chord length as a dimensionless number that runs from 0 to 1. Since the angle of attack is 0°, you need no other correction and the net surface under the c$_{\text p}$ plot is your lift coefficient. Use the results at the six known span positions and interpolate between them.
In principle, the same applies to the drag coefficient, but now you would need a plot which projects the pressure coefficient on a coordinate which runs orthogonal to the flow direction. In inviscid flow, the pressure differences equal out, so it is only the friction-induced changes in the pressure distribution between inviscid and viscous flow which cause drag.
My best advice is to find airfoils with the same pressure distribution and use their drag coefficient values. Make sure you know the Reynolds and Mach numbers, because both have a higher effect on drag than on lift. Some quirks in the pressure distribution can give them away, like the location of the laminar separation bubble on the lower side of the c$_{\text p}$ plot above or the magnitude of the stagnation point pressure coefficient. Regarding the relative thickness of the airfoil: The amount of suction on both sides of an airfoil grows with its relative thickness.

Thanks for the detailed answer here, Peter. It sounds like I'm on the right track for getting the approximate lift coefficient, but I may out of luck for Cd unless I can determine the airfoil somehow. I'll have to look into that.
I'll add that my AoA=0 comment in my original question was for the sake of simplicity - I actually have data for two separate angles (2 and 4 deg). I'm currently attempting to find the normal and axial force coefficients, then will rotate those w/alpha to find Cd and Cl. Are you aware of any methods to find airfoil shape (or z variation) that could use this data?

@user26989: There is free software which allows to reverse-engineer (actually, design) an airfoil from a desired pressure distribution. It is called XFOIL and heavily used by model enthusiasts. I used it years ago to create the images in this answer.

This looks very interesting, thanks for the link (and all the help here!).